﻿#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include "stb_image.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void keypress_callback(GLFWwindow* window, int key, int scancode, int action, int mods);
void processInput(GLFWwindow *window);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec3 aColor;\n"
"layout (location = 2) in vec2 aTexcoord;\n"
"out vec3 ourColor;\n"
"out vec2 TexCoord;\n"
"uniform mat4 transform;\n"
"void main()\n"
"{\n"
"   gl_Position = transform * vec4(aPos, 1.0);\n"
"   ourColor = aColor;\n"
"   TexCoord = vec2(aTexcoord.x, 1-aTexcoord.y);\n"
"}\0";
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec3 ourColor;\n"
"in vec2 TexCoord;\n"
"uniform sampler2D ourTexture;\n"
"void main()\n"
"{\n"
"   FragColor = texture(ourTexture, TexCoord);\n"
"}\n\0";

int main()
{
  // glfw: initialize and configure
  // ------------------------------
  glfwInit();
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

  // glfw window creation
  // --------------------
  GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
  if (window == NULL)
  {
    std::cout << "Failed to create GLFW window" << std::endl;
    glfwTerminate();
    return -1;
  }
  glfwMakeContextCurrent(window);
  glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
  glfwSetKeyCallback(window, keypress_callback);

  // glad: load all OpenGL function pointers
  // ---------------------------------------
  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
  {
    std::cout << "Failed to initialize GLAD" << std::endl;
    return -1;
  }


  // build and compile our shader program
  // ------------------------------------
  // vertex shader
  unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
  glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
  glCompileShader(vertexShader);
  // check for shader compile errors
  int success;
  char infoLog[512];
  glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
  if (!success)
  {
    glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
  }
  // fragment shader
  unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
  glCompileShader(fragmentShader);
  // check for shader compile errors
  glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
  if (!success)
  {
    glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
  }
  // link shaders
  unsigned int shaderProgram = glCreateProgram();
  glAttachShader(shaderProgram, vertexShader);
  glAttachShader(shaderProgram, fragmentShader);
  glLinkProgram(shaderProgram);
  // check for linking errors
  glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
  if (!success) {
    glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
  }
  glDeleteShader(vertexShader);
  glDeleteShader(fragmentShader);

  // set up vertex data (and buffer(s)) and configure vertex attributes
  // ------------------------------------------------------------------
  float vertices[] = {
    //     ---- 位置 ----       ---- 颜色 ----     - 纹理坐标 -
         0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f,   // 右上
         0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f,   // 右下
        -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.0f, 0.0f,   // 左下
        -0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,   0.0f, 1.0f    // 左上
  };

  unsigned int indices[] = {  // note that we start from 0!
      0, 1, 3,  // first Triangle
      1, 2, 3   // second Triangle
  };
  unsigned int VBO, VAO, EBO, TEXTURE;
  glGenVertexArrays(1, &VAO);
  glGenBuffers(1, &VBO);
  glGenBuffers(1, &EBO);
  glGenBuffers(1, &TEXTURE);
  // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
  glBindVertexArray(VAO);

  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

  // 为当前绑定的纹理对象设置环绕、过滤方式
  glBindBuffer(GL_TEXTURE_2D, TEXTURE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  // 读取纹理
  int width, height, nrChannels;
  stbi_set_flip_vertically_on_load(true);
  unsigned char *data = stbi_load("res/texture/container.jpg", &width, &height, &nrChannels, 0);
  if (data)
  {
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
  }
  else
  {
    std::cout << "Failed to load texture" << std::endl;
  }

  stbi_image_free(data);

  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(0);

  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
  glEnableVertexAttribArray(1);

  glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
  glEnableVertexAttribArray(2);

  // note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
  glBindBuffer(GL_ARRAY_BUFFER, 0);

  // remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
  //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

  // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
  // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
  glBindVertexArray(0);


  glUseProgram(shaderProgram);

  // uncomment this call to draw in wireframe polygons.
  // glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
  // render loop
  // -----------
  while (!glfwWindowShouldClose(window))
  {
    // input
    // -----
    processInput(window);

    // render
    // ------
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    // 绑定纹理
    glBindTexture(GL_TEXTURE_2D, TEXTURE);
    glBindVertexArray(VAO);

    // 右下角箱子
    glm::mat4 trans;
    trans = glm::translate(trans, glm::vec3(0.5f, -0.5f, 0.0f));
    trans = glm::rotate(trans, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));
    unsigned int transformLoc = glGetUniformLocation(shaderProgram, "transform");
    glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(trans));
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

    // 左上角箱子
    glm::mat4 trans2;
    trans2 = glm::translate(trans2, glm::vec3(-0.5f, 0.5f, 0.0f));
    float scaleAmount = static_cast<float>(sin(glfwGetTime()));
    trans2 = glm::scale(trans2, glm::vec3(scaleAmount, scaleAmount, scaleAmount));
    glUniformMatrix4fv(transformLoc, 1, GL_FALSE, &trans2[0][0]);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

    // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
    // -------------------------------------------------------------------------------
    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  // optional: de-allocate all resources once they've outlived their purpose:
  // ------------------------------------------------------------------------
  glDeleteVertexArrays(1, &VAO);
  glDeleteBuffers(1, &VBO);
  glDeleteBuffers(1, &EBO);
  glDeleteProgram(shaderProgram);

  // glfw: terminate, clearing all previously allocated GLFW resources.
  // ------------------------------------------------------------------
  glfwTerminate();
  return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
  if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
    glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
  // make sure the viewport matches the new window dimensions; note that width and 
  // height will be significantly larger than specified on retina displays.
  glViewport(0, 0, width, height);
}

void keypress_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
  if (action == GLFW_PRESS)
  {
    switch (key)
    {
    case GLFW_KEY_M:
    {
      static GLenum  mode = GL_FILL;

      // 填充或轮廓
      mode = (mode == GL_FILL ? GL_LINE : GL_FILL);
      // 多边形光栅化模式
      glPolygonMode(GL_FRONT_AND_BACK, mode);
    }
    }
  }
}